The present invention relates generally to satellites or spacecraft, and more specifically, to systems and methods that employ phase change materials to provide thermal control for electric propulsion devices.
The assignee of the present invention manufactures and deploys spacecraft or satellites into geosynchronous and low earth orbits. Electric propulsion systems are used for stationkeeping functions while the spacecraft is in orbit.
Previously known methods for controlling the temperature of electric propulsion systems use a dedicated radiator panel to radiate heat into space while the thruster is firing. This requires a relatively large radiator panel. The more heat that is generated, the larger the required radiator panel must be.
Prior art references disclose the use of phase change materials for batteries, electronic units and for thermal hardening of critical spacecraft components such as solar cells against laser attack from ground or space borne anti-satellite weapons. Other prior art references discusses use of phase change materials as an augmentation to existing passive thermal control sub-system to reduce diurnal temperature swings.
Use of phase change materials sandwiched between heat pipe panels has also been suggested. In general, phase change materials could be used with any thermal system with a variable thermal load. However, in none of the prior art references has there been any disclosure regarding the use of phase change materials in conjunction with thermal management of electric propulsion systems. It has been determined by the present inventors that there are advantages in using phase change materials for thermal control of electric propulsion systems during north/south stationkeeping operations.
It would be advantageous to significantly reduce the size of, or eliminate, the radiator panel used in conventional thermal control systems and methods that are used with electric propulsion systems. Since the radiator panel is usually large and heavy, by eliminating or significantly reducing its size, some mass can be saved.
In addition, the large radiator panel causes other thermal, structure and configuration problems. It would be advantageous to reduced or eliminate these problems. The large radiator panel causes thermal blockage and a backload on other spacecraft radiator panels. If the radiator panel can be eliminated, then the overall thermal performance of the spacecraft is increased.
Accordingly, it is an objective of the present invention to provide for systems and methods that employ phase change materials to provide thermal control for electric propulsion devices.
To accomplish the above and other objectives, the present invention provides for systems and methods that employ a phase change material to provide thermal control of electric propulsion devices (electric propulsion thrusters). The present invention thus provides for a compact, low mass system for dissipating heat created by electric propulsion thrusters.
The present invention uses a phase change material surrounding an electric propulsion thruster, and optionally components surrounding the thruster, to absorb and store the heat that is generated as latent heat while the thruster is firing. Exemplary phase change materials include high-density polyethylene (HDPE), waxes, paraffin materials, and eutectic salts, for example.
The latent heat is dissipated into space, such as by using a relatively small radiator or no radiator at all, after the thruster has stopped firing. The present invention thus controls the temperature of the thruster and surrounding components without using a large radiator panel.
An exemplary method for using a phase change material to provide thermal control for an electric propulsion thruster comprises the following steps. A spacecraft is configured to have an electric propulsion thruster. The electric propulsion thruster is surrounded with a phase change material. The spacecraft is launched into orbit.
When in orbit, the electric propulsion thruster is fired for a predetermined period of time, such as during a stationkeeping maneuver, for example. Heat generated by the electric propulsion thruster is absorbed and stored in the phase change material while the thruster is firing. The stored heat is dissipated into space after the thruster has stopped firing.